Field of the Invention
The present invention relates to an anti-reflection film which is arranged in order to prevent external light from reflecting on a window or a surface of display devices etc. Specifically, the present invention relates to an anti-reflection film applied on a surface of a liquid crystal display (LCD), CRT display, organic electroluminescent display (ELD), plasma display (PDP), surface-conduction electron-emitter display (SED) and field emission display (FED) etc. Among these, this invention relates to an anti-reflection film applied on a surface of an LCD, especially a transmission type LCD.
Description of the Related Art
In general, displays are used under external light whether they are used indoors or outdoors. The external light incident to a display surface is reflected on the surface so that a displayed image is interfered with by the reflected image and the quality of display decreases. Hence, it is necessary to provide a display surface with an anti-reflection function, and further, improvements of the anti-reflection function along with introductions of other extra useful functions are being demanded.
In general, an anti-reflection function is realized by forming an anti-reflection layer having a multilayer structure with repeating high refractive index layers and low refractive index layers made of a transparent material such as metal oxide on a transparent substrate. The anti-reflection layer having this type of multilayer structure can be obtained by a dry coating method such as chemical vapor deposition (CVD) and physical vapor deposition (PVD). In the case where the anti-reflection layer is formed by a dry coating method, while there is an advantage of fine thickness controllability, there is also a problem of low productivity due to a limitation of a deposition process performed in a vacuum chamber, which is unsuitable for mass production. Thus, wet coating methods, which use a coating liquid for forming an anti-reflection layer and make it possible to provide a large display, produce continuously, and reduce costs, attract attention as a forming method of an anti-reflection layer.
In addition, an anti-reflection film in which the anti-reflection layer is arranged on a transparent substrate film generally has a hard coat layer formed by curing an acrylic material which is curable by ionizing radiation as well. The hard coat layer is arranged between the transparent substrate and the anti-reflection layer for the purpose of providing a surface hardness to a relatively soft surface of the anti-reflection film. The hard coat layer is provided with a high level of surface hardness, abrasion resistance, luster and transparency due to the acrylic material.
In the case where the anti-reflection layer is formed by a wet coating method, at least, a low refractive index layer is coated onto such a hard coat layer and is producible with low costs. Thus, this type of anti-reflection film is widely distributed in the market.    <Patent document 1> JP-A-2005-202389    <Patent document 2> JP-A-2005-199707    <Patent document 3> JP-A-H11-092750    <Patent document 4> JP-A-2007-121993    <Patent document 5> JP-A-2005-144849    <Patent document 6> JP-A-2006-159415
It is possible to reduce reflection of external light by arranging an anti-reflection film having a hard coat layer and anti-reflection layer on the surface of a display device and utilizing its anti-reflection function so that a contrast in bright places can be improved. Moreover at the same time, it is possible to display an image more brightly since the visible light transmittance of the anti-reflection film can be improved. The anti-reflection film is also expected to have an energy saving effect due to a reduction of the power consumption of the backlight etc.